3.0: Fix missing use

[sbulen]

Fixes this issue reported in the php error log (not the SMF log) when navigating server settings:

[22-Nov-2023 03:57:41 UTC] PHP Fatal error: Uncaught Error: Class "SMF\Tasks\Db" not found in blah\blah\80van30\Sources\tasks\RemoveTopicRedirects.php:37
Stack trace:
0 blah\blah\80van30\Sources\TaskRunner.php(577): SMF\Tasks\RemoveTopicRedirects->execute()
1 blah\blah\80van30\Sources\TaskRunner.php(209): SMF\TaskRunner->performTask(Array)
2 blah\blah\80van30\cron.php(30): SMF\TaskRunner->execute()
3 {main}
thrown in blah\blah\80van30\Sources\tasks\RemoveTopicRedirects.php on line 37